Seeing a specialist is the best thing to do right now.
Below is a very good link taking you to all kinds of information about cushing syndrome.

Here is a link that might be useful: Cushings

My older dog was diagnosed with Cushings several years ago, so I know loads about it. Due to his advanced age, I opted to treat him holistically and not via the Western medicine chemotherapy.

I am concerned for you and your pup because of the mis-diagnosis of diabetes. Cushings is nothing like diabetes and high blood sugar is not a symptom. Your dog may also have diabetes, but I would think diabetes and Cushing's in one dog would be very, very rare.

Cushings is caused when the body produces excess steriod. This excess production is usually caused by a tumor on the adrenal gland or on the pituitary gland. the tumor is usually benign, but causes the dog to produce cortisole, [sp?] which is a steroid.

The symptoms for Cushings in a dog are excess thirst, excess urination, dramatic increase in hunger, saggy tummy and loose skin. Does this sound like your silky?

Cushings can also be triggered if the dog is receving too much steroid in the form of meds; but this is remedied quite easily by stopping the medicine.

Tumor-generated Cushing's is treated through a form of chemo-therapy or surgery to remove the tumor.

Honestly, I'd take your dog to a different vet and get an entirely new diagnosis/second opinion.

33% of dogs with Cushings disease have concurrent diabetes. The vet did not neccessarily misdiagnose the diabetes or the Cushings. The typical clinical signs of both diseases are very similar. Sometimes there are signs of Cushings in the labwork when the diabetes is diagnosed, but other times not. Usually the Cushings is discovered because the diabetes cannot be controlled with insulin, just like in your son's dog.

You don't necessarily need a specialist to diagnose the type of cushings. If the dog is on steroids, that is obvious- just ask your son if he is giving the dog corticosteroids. Remember that topical steroids can be absorbed systemically too. Dogs with allergies are often given steroid shots to control itching, which can lead to Cushings too. That would be a best-case scenario, because once the steroid administration is tapered off, the disease will go away. Then you are just left with diabetes, which will hopefully stop being refractory to insulin.

The bloodwork to determine the type of cushings is usually a low dose dexamethasone suppression test +/- a high dose dexamethasone suppression test. It is important to know which type of Cushings the dog has because the treatment is different for each. But any vet who can draw blood twice can send the samples to a lab for analysis. The trick is in the interpretation of the results, which can get complicated. Sometimes it's obviously an adrenal tumor, other times it's obviously a pituitary hyperplasia, and sometimes it's really hard to tell. That's when a specialist might be needed. Or your son's regular vet may want to consult because of the concurrent diabetes. Cushings can get very complicated in both diagnosis and treatment, and adding diabetes to the mix really throws in a monkeywrench. Some specialty places can run a endogenous ACTH assay, which is more clear-cut in the diagnosis of PDH (pituitary dependent hyperadrenocorticism) or AT (adrenal tumor), but that blood sample requires very specialized handling and shipping to a certain lab, so it isn't done often. It's probably expensive too.

The concerning note is the blindness. It could be due to glaucoma secondary to diabetes, which can sometimes be reversed. This is pretty common with diabetes. But in rare cases of pituitary carcinoma (bad cancer) which can be a cause of Cushings, sometimes blindness occurs because of tumor interference with the optic tracts. This would be a bad prognostic factor, because 1) there isn't a way to remove a pituitary tumor and 2) that it interferes with the optic tract means it's large already and getting bigger, soon to invade other brain tissue. Hopefully it's just the common glaucoma-related diabetes though.

There is a lot to consider, but really nothing is of any help until the type of cushing's is diagnosed. Once you know whether it is pituitary or adrenal dependent, you have a variety of options for treatment, which either the specialist or your son's vet will discuss. There are pros and cons to every treatment option. Cushings can be managed, but it takes a lot of dedication to the testing, treatment, and monitoring from everyone. And it can get expensive, depending on the type of Cushings and which treatment your son opts for.

In any case, good luck, and please keep us posted.

Meghane, that is very interesting information and not what I was told when I went to the vet that originally diagnosed my dog. So, thank you very much...quite an informative post.

Your post makes me think that maybe I need to take my dog back for a second look about Cushing's. My other vet seemed very sure of herself when she spoke of Cushings and, yet, you have refuted several things she told me. We go to a different vet now, who recently put him on rymadil [sp] for arthritis (he's 15) and his symptoms have improved dramatically. Considering rymadil is a form of NSAID, that was puzzling to me.

Sorry to hijack thread a bit, but wanted to thank Meghane.

Meghane, that is very interesting information and not what I was told when I went to the vet that originally diagnosed my dog.

Hey Cindyb, your above statment is exactly why it's best to go to a specialist in such cases and in this case the persons Vet suggested it, that tells me he/she isn't as up on it to be of adequate help. I always look at it this way, most Vets are GP's and would usually have to consult a specialist anyway, better to go to the person that has more experience with treatments and tests. It may be more expensive to begin with but many times it can save wasted time and treatments that don't work.

cindyb: Rimadyl is OK for a dog with Cushings. It's a NON-steroidal, which is OK. Just be careful of the liver/kidney/GI issues. Steroids are definately to be avoided.

Cindyx: the info is from the vet school, and we get all the weird cases. I'm not so sure that 33% is accurate for a general practice, as things like refractory diabetes are likely to get punted rather than correctly diagnosed as concurrent Cushings at the regular DVM (rDVM). The vets in this area are lucky to have the vet school as a resource, so complicated cases like this can still be managed well by the rDVM if everyone is OK with that situation. The vet school is great with phone consults, but if the case is really complicated or requires special equipment/training then the school is relatively close. Not cheap though. Trust me on that.

so complicated cases like this can still be managed well by the rDVM if everyone is OK with that situation.

Meghane, just to be clear, I have no problem with managing a disease through a GP that is willing to work with a specialist either by phone or referal, and all Vets have this service available to them. I just think the client should also have the knowedge of knowing they have the right to bring a specialist in on any case at any time. I also strongly believe there are some cases that a GP needs to refer out to a specialist immediately for proper testing and I respect those that do.